Polar organic films: Transport gap, charge–dipole interaction and electroluminescence of tritolylamine (TTA) derivatives

The unusually different photoluminescence (PL) and electroluminescence (EL) of an organic film is related to disordered dipoles and charge–dipole interactions that reduce the transport gap of localized electrons and holes in thermal equilibrium. The assignment of EL as direct emission from ion-pairs in films follows the exciplex interpretation of chemiluminescence (CL) in solutions that contain tritolylamine donors.